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Common Fault of Machine Tool and Its Elimination



    Machine tools in the process of use, there are often some faults, such as not timely elimination, will directly affect the production, and will make the precision of the machine tool rapidly decline.Therefore, it is very important to summarize and analyze the fault causes of machine tools and explore the methods of troubleshooting.Machine tools common fault, according to its nature can be divided into the machine itself running abnormal and machining parts produced defects two categories.But the phenomenon of failure is varied.At the same time, the cause is often a combination of many factors.Generally speaking, there are the following causes of failure:

    The machine itself of the mechanical parts, electrical components, hydraulic equipment and other work failure, or some parts wear badly, accuracy is out of tolerance and even damage.The machine tool is inaccurately installed.Improper daily maintenance.Unreasonable usage.The original design of the machine tool is imperfect or unreasonable.

    In the daily work, the fault phenomenon of machine tool is relatively obvious.Such as machine parts damage is due to a serious accident (such as a crash, etc.) caused by the machine tool operation is not normal, or even stop the rotation, etc. But most of the fault is through the machining parts can not reach the precision, there is some kind of defect and show.The following is a brief description of common faults and possible defects of machining parts.Common machine tool faults are:

    1,Bearing Overheating

    The shaft parts of machine tools, especially the spindle, are generally assembled into a rolling bearing or sliding bearing, and rotating at a very high speed sometimes will produce a high amount of heat.This phenomenon, if not eliminated in a timely manner, will lead to overheating of the bearing, and the corresponding part of the machine tool temperature and thermal deformation, which not only affects the accuracy of the machine tool itself and machining accuracy, and will burn out the bearing.The causes of heating of the main bearing and its elimination methods are shown in table :

The cause of the problemThe solution
Rolling bearing
(1)Low bearing accuracySelect the specified precision grade bearings
(2)The main shaft bending or box hole different coreRepair spindle or box
(3)The belt too tightAdjust the belt to make it properly tightened

Bad lubrication

Lubricate with specified grades and clean properly
(5)Low assembly qualityImprove assembly quality
2Sliding bearing
(1)Improper fit clearanceAdjust the clearance


Spindle bent or box bore with different coresRepair spindle or box
(3)The working surface geometry of spindle and bearing is incorrectRepair the spindle and bearing to make the working surface smooth and the geometry correct
(4)Bad lubrication

    Bad lubrication is easy to overlook a problem in work, but it is a very important work, is the purpose of the machine tool lubrication is in accordance with the provisions, to the machine tool parts injection of relative motion need lubricating oil, make the ideal oil film formed between parts, so as to reduce wear to a minimum, reduce the wastage of the machine tool energy, keep the accuracy of machine tool processing, prolong the service life of the machine tool.If the lubrication is not timely, it will make the precision of the machine tool in a short period of time sharply decreased, service life is greatly shortened, resulting in invisible wear, so the lubrication of the machine tool is an important link to do a good job in machine tool maintenance.Here are a few ways to change poor lubrication. First according to the provisions of the accurate and timely lubrication of the machine tool lubrication parts, do according to the provisions of the oil hole refueling; Refueling according to the specified time, according to the specified grade, according to the specified quantity.The operator and the person responsible.Namely fixed point, fixed point, fixed amount, fixed person. 


     2, Machine tool vibration 

    Machine tool vibration in machining process, it is inevitable, but when the vibration will not only reduce the machining accuracy of work piece, affect productivity, aggravate wear of the machine tool friction pair, and the tool life, especially for cemented carbide, ceramics, such as brittleness tool material is particularly significant, cause vibration of the machine tool and its elimination method are shown in table .

No.The cause of the problemThe solution
1High - speed rotating parts unbalancedThe balance parts
2Motor rotation imbalanceBalance the rotor of the motor
3Eccentric workpiece to be machinedTighten the workpiece and find the correct alignment
4Defective belt jointReplace
5Bad gear engagementGear accuracy shall be in accordance with the specifications, or when repaired or replaced
6The anchor bolts of the machine tool are loose and not properly installedThe machine should be installed accurately, firmly and reliably
7The environment vibratesThe installation of machine tool and the impact of the equipment should be a certain distance, or open anti-vibration ditch
8Poor lubrication and coolingLubrication and coolant should be sufficient
9The cutting is discontinuous, the cutting dosage is improper, the cutter geometry Angle is improper or blunt, the material being machined is not easy to cutAppropriate cutting parameters, use advanced tools, for discontinuous cutting, should improve the tool Angle or avoid reducing the impact of the cutting process
10Machine tool stiffness differenceSelect high-quality machine tools


     3, Noise

     After the machine is started, due to the rotation between the motion pairs or reciprocating linear sliding, periodic contact and separation, between them due to mutual motion and produce a certain vibration.In addition, the entire transmission system of the machine will resonate.Therefore, no matter how reasonable the structure of any machine, how accurate assembly, how appropriate operation, once started will produce noise.If the sound is rhythmic and harmonious, it is normal; if the sound is too loud and harsh, it is abnormal.Noise is the forerunner of machine failure, so if abnormal phenomenon should be stopped immediately, troubleshooting before production.

     In general, the noise increases with the increase of temperature, load, wear and poor lubrication.The following describes the main shaft and bearing noise causes and elimination methods.

No.The cause of the problemThe solution

Spindle and rolling bearing

(1)Bearing imprecisionImprove the assembly quality, make the clearance suitable, after the assembly with the hand should be flexible
(2)Low bearing accuracySelect bearings with high precision

Bearing parts are badly worn or worn

(4)Spindle nose and rear journal and spindle box with different coresRepair spindle and headstock so that they can be used concentric
(5)Bad lubricationAccording to the provisions of the selection of lubricating materials, and appropriate, clean.
2Spindle and sliding bearing
(1)Fit clearance is too large,Adjust the clearance
Spindle nose and rear journal and spindle box with different coresRepair spindle and headstock so that they can be used concentric.
(3)Bad lubrication

Use proper, clean lubricants.

     4, Oil leak

Oil leakage of machine tools is a common fault in the daily work of machine tools.It not only wastes oil, directly causes economic losses, but also affects the working performance of the machine tool. Meanwhile, long-term oil leakage will also bring adverse consequences to the installation foundation of the machine tool.Therefore, we should attach importance to the "leakage control" work of machine tools.To carry out investigation and research, find out the oil leakage site, analyze the causes of oil leakage, take measures to solve.Table lists the common causes of oil leakage from multiple machine tools and their elimination methods.

No,The cause of the problemThe solution
1Bad casting, the casting itself has sand holes dark joints, oil tank body due to collision caused by cracks.Fix the leak with an epoxy adhesive and iron powder filler, such as seriously replacing the fuel tank.
2Oil leakage from ruptured pipeReplace the tubing
3Oil tank cap joint surface uneven, lax sealScrape or grind the joint surface
4Leaks from screw holes, various handles and oil standard observation holes.Can increase the pad oil - resistant rubber ring, cowhide pad and other seals.
5Add to much oilFill the oil according to the oil standard.
6Damaged or lost sealing performance of the original sealReplace the seal
7Damage to part or loose nut at joint.

Replace damaged parts and tighten nuts.

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